It is known from various documents, also including some from the same Applicant, to use flexible protection elements of parallelepipedal form in order to immobilize and protect, for example, underwater pipes, canal banks and beds. Those elements comprise a flexible external cover which coats a gabion which is constructed from metal material and is filled with a mixture composed of bitumen, sand and stones or pebbles, so as to obtain elements having a high unit weight. Those protection elements, once made up, must be lowered into water by means of handling machines, such as cranes, mechanical arms, and the like. In order to facilitate the above-mentioned laying, operations are known for producing mattress type protection elements comprising support elements which facilitate, when in use, the handling thereof.
One of the main limitations of the elements of known type is constituted by their great thickness and their heaviness, which make the installation operations extremely complex and troublesome.
Another limitation of the elements of known type is constituted by their limited overall dimensions, which are linked to the dimensions of the gabions and/or the forms which are used for constructing them.
An object of the present invention is to provide a protection element and filter of the mattress type which has significantly reduced weight, which allows easier installation, which has overall dimensions which are variable in accordance with the type of application necessary and which can successfully constitute protection elements and a filter without longitudinal discontinuities, for example, but in a non-limiting manner, up to 200 linear meters.
Another object of the present invention is to provide a protection element and filter which is economical, easy and rapid to construct and which therefore allows a substantial saving in terms of the time and cost of installation.
In order to achieve the above-mentioned objects, the present invention relates to a lightweight protection element and filter of the mattress type as described below.
One of the main advantages of the present invention is constituted in that the protection element further comprises a three-dimensional internal structure with a high cavity index, in which filler material is inserted, such as gravel, silt, finely crushed stone, or any other natural granular element which is available in situ. That advantageous feature avoids the need to create internal diaphragm openings for stabilizing the filler material.
According to another particularly advantageous feature, the mattress type element also comprises a double layer of geotextile material, for example, an upper layer and a lower layer, which, being connected to the three-dimensional internal structure, allow the protection element to act as a filtering element and, at the same time, to remain fitted closely against the terrain to which it is applied owing to the ballast weight of the granular filler material.